Electron-discharge-tube amplifier system



5H. l. DANZIGER Er Al- Filed Aug. 1, 1924 ELECTRON DISCHARGE TUE-E AMPLIFIER SYSTEM Patented oet.` 2s, l1930 i UNITED sfrArEis nanou) I. rnnivzrsnn, orfnnw Yon-x, 1v.

Y1, ANDLLEsrnRL JONES, on loanni;rin;

d NEW 'JERSEY-Y nnEorRoNhDIsCHARGE-TUBE 'mulufirrnnl SYSTEM f f .Application i led August A 1,

. This invention l relates tof an amplier system, and more particularly to electron -disf charge tube amplifier circuits; land has special reference to the provision of an improved .5 switching system for varying the number of YVsteps or stages of amplification in cascade amplifier circuits.` y I In cascaded electron discharge tube ampli* fierV systems of the type employed, kfor kex- -1o ample, in radio receiving-circuits, itis common practice where a stageV of amplification is desired to be added for further amplifying c y the received signals to shift the receiving output circuit such as the phones from one eleci5 tron discharge tube to the next succeeding tube, and-to interpose a transformer` between the tubes where transformer coupling is used. Inthis practice the added step'or stage of amplification is added onto a prior stage, with the result that such prior stage is shiftedifrom V al terminal or ending position yto an intermediate 4positiont This shifting of the ter-4 minal stage of amplification presents a nume ber'of'disadvantages, and it is highly desirableon the contrary to maintain the terminal or last amplifier stage in fixederelation to the receiving output or phone circuit during any and all changes-in the number of stages of amplification used. 1 f

, In .a multi-stage audio frequency amplifier, forenample, itis always desirable tosecure maximum volume with the'minimum number of stages of amplification, this because each stage-of amplification, introduces some distortion; and the maximum volume can bev produced best without distortion by lusing ka tube of large power or several tubes of smaller power in parallel, or several tubes in pushpullrelation for the last or ending receiving 40 output such as kthe vtelephone loud speaker cir-r cui-t.V TWhere a telephone loudspeaker, howkever,is switched from one electron discharge tube to the next in accordancewith this common practice, if the highest efhciency should be desired tov be maintained, 'it would become necessary to yprovide the large-power tube or tubes in push-pull relation fora plurality of stages ofv amplification, and this would be uneconoinical, both as to first cost and maintey :$0 nance. Where, onzthe other hand, the tubesin 1924K. senat No.' 729,448. .z

successiveamplification stages have notA 'Y same powerl characteristics, the shifting of the output orphone circuit renders the system inefficient. To provide a systenr which may bev 'efficient land economical, is desirable.y to lmaintain a ixedrelationbetweenthe phone circuit'and the highpower tube.stage,fkeep ing such stage always as the ,endingtor ter-` minal stage of the set); and our present inventev tion has foil its primel object the provision of an improved switching systemingwhich'tlie last or terminal amplification stage is always maintained in fired relation tothe ltelephone loud speaker circuit, and in Whichthe added stage is interposed or inserted imposition in advance of the phone circuit or amplification stage. Y In aA switching system the terminal where the added stage is interposed in advancey of the ending stage,itis highly important when a step of amplification iis added toor removed fromthe system,to prevent the transferring,V changing or switching ofhighlpotenti'al input or grid leads, and it-.is highly ladvantageous andjdesirable that the switching be effectedonly transferring or changingfthe outputl .orplate leads. 0f the moreimportant advantagesregsiding in` 'their switching l.of output leads are the simplicity ,of the switching arrangement this ymakes possible'and the factthat there? active' effects dueto the wiresleading tothe. switch gear `are much yless when these wires .are outputleads than kwhen they are input leads. This' latter consideration. is, of en? tremefimportance in,L the 4:application of'` the system to radio frequency Q amplifiers. V. The radio frequency amplificationmust be exact? ly balanced as to capacitivereactive effects, and in' changing thefnumber of stages by switch-ing the f input leads, thisv balance L is disturbed,jwhereas itis disturbed'to a much y less .f degree .when'switching the ,outputleadsf vA further-consideration `of importance inthe leads, whereas it is affected byy switchingthe input `leads 5 and ythe ,f detuning, effect in .the

radio frequency amplifier,assumes'verylarge tenna circuit, the switching of the antenna capacity from one input circuit to another input circuit resultin in large changes of tunlng. A prime desi eratum, therefore, of our present invention, comprehends the rovision of a switching system for cascade electron discharge tubes or devices in whichk the addible stage is interposed or inserted in 'tion inadvance of or prior to a fixed endlng stage, and in which the circuitV changes are all produced by transferring or shifti the output leads only. s f

o the accomplishment of the foregoing and such other objects as will hereinafter ap ar, our invention consists in the eiements an n their relation one to the other, as hereinafter particularl described and sought to be ned in the c aims; reference being had to the accom anyin drawing which shows the preferredpembo iment of our invention, and 1x1 which: The figure is av wiring diagrammatic view of the im roved switching system of our invention, diesame being shown applied as a multi-stageV audio Aamplifier for radio receivinr circuits. f

Re crring now morein detail to the drawings, `we show the principles of our invention exemplified in a multi-stage audio amplifier system having the detector sta e D which is preferably of the electron disc arge tube type including the electron' discharge device e, to which detector stage is connected a terminal amplifier stage A2 comprising one or a plurality of electron discharge dev1ces e2, e 2 and a transformer t2 having a primary 'p2 and a secondary s2 for coupling the electron discharge device or tube to a preceding stage, and an addible amplifier stage A1 which comprises the electron discharge device or tube e1 and the coupling transformer t1 having the rimary p1 and the secondary s1, the said ad ible amplifier stage A1 being insertable or interposable in advance of or in position prior to the terminal amplifier stage A2. Where the system consists in multi-stage audio amplifier circuits, as shown in the drawings, the detector stage D may be connected to any yhigh frequency circuit, as for example tothe output of a tuned radio frequency system such as is disclosed in the conding applicationof Lester L. Jones, Ser. 60. 716,124, filed May 27th, 1924, the electron dischar vdevice e of the detector stage being provi ed with an input circuit -z and an out ut circuit o, the input circuit z being in uctively coupled yto a radio frequency amplifying stage bymeans of a variotransformer V having the primary 10 and a variable secondary 11. The input circuit i is connected across the gridf12 and filament 13 of the electron vdischarge device e, the said input circuit com` risinga conductor 15 connccted to a con uctor 16 forming part of a filament circuit f, conductor 16', secondary 11 of variotransformerrV, conductor 17, conductor 18, the integrating device 19, and conductor 20 connected to the grid 12.k The output circuit o of the electron discharge device e comprises the conductor 21 connected to the anode or plate 14 ofthe electron discharge device, the conductor 22 which is selectively connectable to either of the amplifier stages A1 or A2, and more specifically to the primary circuits p or p2 thereof, by means which will be described more in detail hereinafter, the circuit being completed by the conductor 23 connected to the positive terminal of the battery B, the battery B, conductor 24 which connects the negative terminal of the battery B to the positive terminal of the battery A, the latter battery being the source for energizing the filament circuit fas is well known to those skilled in the art. Preferably bothy the inputcircuit z' and theloutput circuit o are shunted'by the condensers 25 and 26 respectively. 2

The ending or terminal amplifier stage A2 includes, as heretofore stated, the electron discharge devices or tubes e2 and e2 whichare arranged in parallel, each being provided with lament 132, the grid 122, and the plate 142, the filaments being both heated to incandescence by means of a filament circuit f2, the filaments being connected `in multiple to this circuit by means of theconductors 27-28 and 29-30, the grids being connected in multi le by means of the condiiictors 31 and 32 Whic are'connected in the input circuit i2 which includes the grids, conductors 3l and 32, 'conductor 33, secondary, 82, 'conductor 34,

vfilament resistance 35, conductors 27 and 29,

and the filament 132.

The plates or anodes 142 of both electron dischargev devices e2 and e2 are also connected in multiple by means of the conductors 36 and 37, and are arranged in the output circuit o2 which includes the anodes or plates, the conductors 36-37, conductor 3,8, a receptacle for receiving a telephone connection or jack, which receptacle includes the contact 39 and base contact 40 attachable to the panel 41, lthe said output circuit being completed by the conductor 42 conductor 23, the battery B, and conductor 24 connected to the battery A and the filament 132. `When the telephone jack is inserted in the receptacle 39-40, it will be seen ythat it is a characteristic of the terminal amplifier stage A2 that the grids and anodes are permanently connected to the input and output circuits of the amplifier stage. `The addible amplifier stage A1 which includes-the electron discharge device el and the transformer t1 is provided with an input circuit z', which includes the grid 121, the conductor 43, the secondary 81 of the transformer t1, the conductor 44, conductor 45, the filament rheostat`46, and filament y131, and'is further provided with an outputk circuit o1 which includes the plate 141, the conductor A47, con

il," and the filamentf 133.

d'l'ictor lS, primary p2 'ofthe transformer t2,

conductor 49l condi'ictorsV 50 and 23, battery B', conductor 24, positivetermi-nal of battery It' will be noted that in this faddible amplifier stage whether or not thestage is in'or out of circuit, the` grid 121is permanently connected inthe input circuit 'il and the plate 141 is permanentlyv 71connected in the outputv circuit 01. v n As heretofore stated, a prime desideratunr of our present invention comprehends the` provision of a switchinggsystem forcascaded amplifier circuits in whichthe -addible stage isfinterposed vor inserted in position in advance of or prior toan ending stage so as to maintain the endingY ory terminal stage in fixed relation to the final output or phone circuit, and in which the circuit changes are Cil al'l produced by transferring or shifting the loutput leads onl-y so as to inhibit any reactiveeffect-s that would be due totransferring or changing input leads.V To accomplish the desired-ends, the terminal and 'add-ible amplifier'stages A2 and Alare connected as hereinc before described, and there is provided a switch mechanism generally designatedas S which functions to permit the addible yampliiierstage to be inserted or interposed betweenV an iuitialcircuit such as the output circuit 0 anda second output circuit such asthe amplilier'ou'tput o1, the addible amplifier stage being switched in andvout of circuit by the break-ing-l andmalring of circuit connections between' the said amplifier output circuit and the saidf'initi-al output circuit.`

' The switch mechanism S inthe preferred construction comprises; a common contactrlv connected to the conductor 22y of the initial output circuit o, a contact 52 connected by meansof a conductor 53 to the primary p1 ofthe transformer t1, the said primary beino'v connected in turn by means of the con-` ductors '54:' and 23 to the positive terminal ofv the battery Bgand a third contact connected by means of the conductors 56 and 48 to the primary p2 of the transformer t2. Preferably-the contacts 5l and'52 are normally inconductive relation bythe closing of the switch points thereof, as clearly shown in the drawings, and the contactsv 51- and 55 are in open circuit` relation so that when the switch button 57, which'is mounted Ona part of the, panel 4l, is inthe position shown in the drawings, withy the cam element 58 thereof in positionrrto releasefthe resilient contact device 59 connected to the contact 5l, both amplifier stages A1 rand A2' are arranged in series or cascade, and are connected to the detector stage D. y

hen, however, the button 57, which may be provided with the indicator 60, is given apartial rotation, the spring contact 59 is moved to open the contacts 5l and 52 and to connect the contacts 5l and 55 in circuit closing relation, this operation being effective foryremoving the? amplierf stage A1! andv for directly connecting theflou'tput of thefdeteetor Dto theoutp-ut circuit 01'andmorefs'pecitlcal'` ly to the primary p of the terminal amplifier stage transformer. l

- lf ith this described construction, it'wiflfl be seen that the terminali amplifier stage A2: is always maintainedk fixed relatively* tothey phone circuit, and that during the switching ofi thegadfdlible amplifier stageA1v in and out of circuit, theinput circuits il and 2 are maintained invariant, theinitial circuit being-` switched between points in the primary trans?. former circuit ofY the terminal, ampli-fier stage and the primary transformerk circuit ofthe addible amplifier stage. Thus the grid: leads v of allfstages may be left as short as possible owingk to no rconnection' of such leads to fthe switch. gearing, minimiz! ingv capacitive feed back reactions due to the capacity between the grid and plate circuits of the tubes, capacitive feed bach vari-g ations being more pronounced by changes in circuit connections in the grid or input circuits than inthe plate or output circuits due to the step-up ratio in the transformers and the relativiely high potentials in t-he gridcircuits produced thereby. The permanent con- -nection ofthe last two outputcircuits toftheir tubes and the switching of the high potenial output vleads also eliminates a considerable number of wires and telephcnejacks, thereby lowering the cost of the switching systemv andY making the same more flexible. Vhere vthe system is employed for radio frequency am` pliiication, not only are capacitive feed back effects minimized and the balance of thefradio frequency amplifier maintained, but the tuningwof the radio frequency circuits-s substantially unaffectedV by switch operations. TWhile. we have shown this switchingy system appliedto a two-stage audio amplifier and applicable to'a two-stagelradio amplifier,- it will 'be apparent that the system may be applied to one or multistage amplifier sys.-

provide the normally open contacts. 61 and (l2-which are adapted to be closed by the engagement of the-insulatingbutton 63 with the l ductors 66 and 67, the connection to the filament circuit f being by means ofthe conductorsy 66, 68, 69 and 70, and the connection to the filament circuit f1' being by means of the conductors 66, 68 and 71, contacty 59, a complemental contact 72, and conductor 7 3. The complemental contacts 59 and 72 are controlled by the cam device 58 of the switch button 57 which controls the switching in and out of circuit of the addible amplifier stage A1, sothatthe filament circuit f1 of suchstage may be controlled simultaneously with the control ofthe addible or intermediate amplifier stage. The negative side of each ofy the filaments is ypreferably permanently connected to the negative terminal of t-he batt-er A, the connection of the filament 13 being y means of the conductor 7 4, rheostat 75, and conductors 76, 77, 78 and 79; the connection ofthe filament 131 being by means of the rheostat 46, conductors 45, 80 and 7 9; and the connection of the filaments 132 being by means of the rheostat 35 common thereto and the conductor 81.

The manner of making and using the amplifier switching system of our invention and the many advantages incident thereto will in the main be fully apparent from the above detailed descri tion of the structure and operation thereof.) It will be further apparent thatwhile We have shown our invention in the preferred form, many changes and modifications may be made in the structure disclosed Without departing from the spirit of the invention, defined in the following claims.

We claim: f

1. An electron discharge tube amplifier system comprising an initial circuit, an output circuit connectable to the initial circuit for receivingy energy therefrom, a stage of amplification including an electron discharge device having a grid and anode and a transformer having primary and secondary ci rcuits, the grid kof the electron discharge device being permanently connected to the said secondary circuit and the anode of the electron discharge device being permanently connected to the output circuit, and mechanism for interposing said stage of amplification between the initial circuit and the output circuit comprising means for switching the said initial circuit from the said output circuit to the primary circuit of the transformer.

2. An electron discharge tube amplifier system comprising an initial circuit, a terminal stage of amplification connectible to the initial circuit and including an electron discharge device having a grid and anode and a ytransformer having primary and secondary circuits, and an addible stage of amplification also including an electron discharge device having a grid and anode and a transformer having primary and secondary circuits, the secondary circuit of each transformer beingfpermanentl connected to the grid of the electron discL arge device associated therewith, the anode of the addible stage being permanently connected to the primary circuit of the terminal sta e, and mechanism for adding or removing t e addible stage of amplification comprising means for switching the said initial circuit between points in the primary transformer circuit of. the terminal stage of amplification and the` primary transformer circuit of the addible stage of amplification.

3. A11 electron discharge tube amplifier system comprising a terminal electron discharge amplifier having an input circuit and an output circuit, an intermediate electron discharge amplifier having an input circuit and an output circuit, an initial output circuit and mechanism for adding or removing the intermediate amplifier comprisin means for changing the circuit connections etween the output circuit of the intermediate amplilier and the initial output circuit without interrupting the outputcircuit of the yintermediate amplifier. f

4. An electron discharge tube amplifier system comprising a terminal electron discharge amplifier having permanently connected input and output circuits, an intermediate electron discharge amplifier also having permanently connected input and output circuits, the output circuit being coupled to the input circuit of the terminal amplifier, an initial output circuit and mechanism for adding or removing the intermediate amplifier comprising means for changing circuit connections betweenthe output circuit of the intermediate amplifier and the initial output circuit.

5. An electron discharge tube amplifier system comprising an electron discharge amplifier having an in ut circuit and an output circuit, said ampli er output circuit having a ytransformer primary permanently oonnected to the anode of the amplifier, an initial output circuit coupled to the amplifier input circuit, and mechanism for switching the amplifier in and out of circuit comprising means for breaking and making circuit connections between the amplifier output circuit and the initial output circuit without interrupting the amplifier output circuit.

Signed atNew York city, in the county of New York and State of New York, this 30th day of July, A. D. 1924.

HAROLD I. DANZIGER. LESTER L. JONES. 

